1). Field of the Invention
This invention relates to an apparatus for testing a substrate having a plurality of terminals, and to a method of testing a substrate having a plurality of terminals.
2). Discussion of Related Art
Electronic circuits are often made by manufacturing a plurality of electronic devices such as transistors, capacitors, diodes, etc. in and on a semiconductor wafer. The devices are interconnected with one another in an integrated circuit by metal lines that are deposited on the wafer. A plurality of terminals are formed on a surface of the wafer and are connected to the metal lines. Electric signals can be provided to or received from the integrated circuit through the terminals.
A number of the integrated circuits are usually formed in and on a single wafer. The integrated circuits are located in the form of dice in rows and columns on the wafer. The wafer is subsequently sawed so that the dice are singulated from one another.
Before the wafer is sawed, the integrated circuit of each die is tested for defects. A probe card having a plurality of probes is used for making an electrical connection to the terminals. Each probe has a contact region which contacts a respective one of the terminals. The probes are connected to an electrical tester. The electrical tester provides signals through the probes and the terminals to the integrated circuit, and receives signals from the integrated circuit through the terminals and the probes.
Due to many factors, some of which are discussed hereinbelow, proper contact between the probes and the terminals is often difficult to obtain. Contact regions of the probes may, for example, be located in one plane and the terminals may be located in another plane which is not parallel to the plane of the contact regions. When the terminals and the contact regions are moved into engagement with the terminals, some probes may create more force on some terminals than others. In more extreme situations proper contact between a probe and a terminal is not provided. Other problems such as rotational or positional misalignment may also occur.